# How can I calculate the density of a gas?

Apr 15, 2014

Start with the units of density…grams (or mass) per unit volume. For gases, since they are usually very low density, that unit volume is usually in liters.

So, once you know the mass and volume, just divide them.

EXAMPLE

A syringe with a mass of 45.861 g contains 50.0 mL of carbon dioxide at the lab temperature and pressure (1.00 atm and 20 °C). If the empty syringe has a mass of
45.953 g, what is the density in grams per liter of the CO₂ under laboratory conditions?

Solution

Mass of CO₂ = (45.953 – 45.861) g = 0.092 g

Density = $\left(\text{mass")/("volume")= (0.092" g")/(0.0500" L}\right)$ = 1.80 g/L